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I would like to know if it is possible to make an engraving or burning moon's surface by focusing high energy laser beam from earth?

uhoh
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user0193
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    This sounds like a wild hypothetical out of left field. Is there a basis for your question? If so, you may want to expand your post, or it may get closed for needing clarity. – called2voyage Feb 16 '21 at 22:21
  • I remember something (probably false) about Pizza Hut (or some other corporation) wanting to carve their logo into the Moon. Idk, but I think the idea is gross violation of cosmic proportions. I hope nothing like that is ever realized. – BMF Feb 16 '21 at 23:01
  • Also, not sure about the specifics, but the dark patches on the moon are preciously molten basaltic plains. If you magmatize large swathes of lunar surface (with a laser) you could discolor it and that discoloration could be visible from Earth. – BMF Feb 16 '21 at 23:24
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    slightly related and pretty cool!: Was there once a semi-serious space-art project planning to use solar reflectors to put a spot of light on the crescent Moon? The problem with "Is it possible to..." questions is that it is often possible but only with an extreme amount of money, time and effort. Of course this is possible, but it might require to the GDP of a medium sized country and a few decades to build enough lasers to do it. – uhoh Feb 17 '21 at 00:53
  • If you adjust your question to ask something more specific; a certain diameter spot, a certain intensity (e.g. how many kilowatts per square meter, etc. then maybe a practical answer is possible. There are certainly lasers that have been fired at the moon for laser ranging experiments for decades, but those end up quite large and low intensity by the time they get there. Thanks! – uhoh Feb 17 '21 at 00:55
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    https://www.imdb.com/title/tt0813112/ – uhoh Feb 17 '21 at 03:10
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    @uhoh: That was the first thing I thought of when I saw the question title. – Fred Larson Feb 18 '21 at 17:54
  • @FredLarson credit goes to (at)geoffc who mentioned it first (now deleted) I just added the supporting link – uhoh Feb 18 '21 at 19:50

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The answer is no. Too much power would be required. Even if the power was somehow available, sufficient power to have an effect on the Moon would heat Earth's atmosphere to such an extent that oxygen and nitrogen would react. Such atmospheric disturbance would interfere with the laser.

Even the worlds most powerful laser would have no noticeable effect.

Slarty
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  • so technically one would need 4 YW to engrave on the moon, which is not possible with our current technology. Right? – user0193 Feb 18 '21 at 16:02
  • Right, many many orders of magnitude and is not possible with our current atmosphere either. – Slarty Feb 18 '21 at 19:29
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Rather than worry about cost, legality, etc. , let me try to discuss the physics of focussing any beam (regardless of power) on the Moon's surface.

The biggest problem is that of atmospheric turbulence destroying the wavefront. In essence, you need to do "reverse adaptive optics," measuring the atmosphere and bending the outgoing wavefront so that the atmospheric effects produce a clean wavefront as the beam exits the atmosphere. This is what the various military anti-missile laser programs (Airborne Laser, e.g.) dealt with.

Next, you need to look at the usual diffraction problem: what kind of beam waist /focus can you achieve at that distance, given a practical size transmission aperture? (Calculating this Airy Disc pattern is left as a homework problem :-) ) .

Now that you've done all that, if you really want power levels sufficient to vaporize or sinter moon dust/rock, you'll need to ensure the beam power density, $\frac{W}{m^2}$ , is low enough that you don't instigate atmospheric heating, which would distort your beam again.

Carl Witthoft
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    And the answer is? – user2705196 Feb 17 '21 at 13:57
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    @user2705196 The answer is 'How much money do you have?' – Carl Witthoft Feb 17 '21 at 14:42
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    Would all the money in the world be enough? – user2705196 Feb 17 '21 at 15:07
  • You'd think atmospheric heating is what you'd want. Hot air is less dense than cold air, so there'd be less air to stunt your laser. And with enough power you could get a column of super-hot atmosphere at near-vacuum, right? – BMF Feb 17 '21 at 17:29
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    @BMF it's not attenuation, it's the nonuniformity of densities that causes wavefront degradation. – Carl Witthoft Feb 17 '21 at 19:26
  • @user2705196 I estimated "the GDP of a medium sized country and a few decades" but chose not to defend it as an answer. – uhoh Feb 18 '21 at 01:13
  • Just for more fun: place your laser in GEO , or maybe a constellation of lasers, bounce them off a large primary mirror also in GEO. – Carl Witthoft Feb 18 '21 at 13:02
  • So it is theoritically possible to engrave on the moons surface if we deal with things like "reverse adaptive optics", "Airy Disc pattern" and "beam power density" ? Is there anything else you might consider? – user0193 Feb 18 '21 at 16:09